the B-ring of sterols to produce a reactive radical intermediate which can quickly react with another thiol radical to form the last labelled derivatives. This labelling reaction can rapidly complete only within 1.5 min. Absorbingly, the NCPM-d -SH and NCPM-d -SH labelled derivatives of sterols can produce two specific 0 2 m z product ions (PIs) containing different isotope tags at / of 431.6 and 433.6 via collision induced dissociation, which were employed to develop the multiple reaction monitoring (MRM) mode-based analysis. According to the specific mass differences with a fixed value, the peak pairs with similar retention times can be easily extracted from the two PIs spectrums and designated as the candidates for the identification of sterols. NCPM- d -SH and NCPM-d -SH labelled derivatives of sterols can be readily distinguished from their several ion 0 2 chromatograms. Thus, sterols from two samples labelled by different isotope tags were ionized at the same conditions and measured respectively, providing excellent identification and precise quantitation by compensating the matrix effect and instrument fluctuation during MS-based analysis. The detection sensitivities of thiol-containing drugs improved by 53.5 - 560.3-fold due to NCPM-labelling. The limits of detection (LODs) - 1 - 1 and the limits of quantitation (LOQs) were in the range of 0.15 -0.40 μg kg and 0.50 -1.30 μg kg , respectively. Using the developed method, we quantitatively profiled five sterols in vegetable oils with good applicability. As promising, the proposed thiol radical-based CIL strategy is a potential platform for the quantitation of sterols.

Yu, Y., Yang, J., Zheng, L.-Y., Sheng, Q., Li, C.-Y., Wang, M., Zhang, X.-Y., McMinn, A., Zhang, Y.-Z., Song, X.- Y., Chen, X.-L., 2020. Diversity of D-amino acid utilizing bacteria from Kongsfjorden, Arctic and the metabolic pathways for seven D-amino acids. Frontiers in Microbiology 10, 2983. doi: 10.3389/fmicb.2019. 02983.

https://www.frontiersin.org/article/10.3389/fmicb.2019.02983 D-amino acids (DAAs) are an important component of the refractory dissolved organic matter pool in the ocean. Microbes play a vital role in promoting the recycling of DAAs in the ocean. However, the diversity of marine DAA-utilizing bacteria and how they metabolize DAAs are seldom studied. Here, by enrichment culture with DAAs as the sole nitrogen source, bacteria of 12 families from three phyla were recovered from surface seawater and sediment from Kongsfjorden, Arctic, and seven DAA-utilizing bacterial strains were isolated. These strains have different DAA-utilizing abilities. Of the seven DAAs used, Halomonas titanicae SM1922 and Pseudoalteromonas neustonica SM1927 were able to utilize seven and five of them, respectively, while the other strains were able to utilize only one or two. Based on genomic, transcriptional and biochemical analyses, the key genes involved in DAA metabolism in each strain were identified and the metabolic pathways for the seven DAAs in these marine bacteria were identified. Conve rsion of DAAs into α -keto acids is generally the main pathway in marine DAA-utilizing bacteria, which is performed by several key enzymes, including DAA oxidoreductases/dehydrogenases, D-serine ammonia-lyases, D-serine ammonia-lyase DSD1s and DAA transaminases. In addition, conversion of DAAs into LAAs is another pathway, which is performed by amino acid racemases. Among the identified key enzymes, D-serine ammonia-lyase DSD1 and Asp racemase are first found to be employed by bacteria for DAA utilization. These results shed light on marine DAA-utilizing bacteria and the involved DAA metabolism pathways, offering a better understanding of the DAA recycling in the ocean.

Zander, T., Haeckel, M., Klaucke, I., Bialas, J., Klaeschen, D., Papenberg, C., Pape, T., Berndt, C., Bohrmann, G., 2020. New insights into geology and geochemistry of the Kerch seep area in the Black Sea. Marine and Petroleum Geology 113, 104162.

http://www.sciencedirect.com/science/article/pii/S0264817219306142 High-resolution 3D seismic data in combination with deep-towed sidescan sonar data and porewater analysis give insights into the seafloor expression and the plumbing system of the actively gas emitting Kerch seep area, which is located in the northeastern Black Sea in around 900 mwater depth, i.e. well within the gas hydrate stability zone (GHSZ). Our analysis shows that the Kerch seep consists of three closely spaced but individual seeps above a paleo-channel-levee system of the Don Kuban deep-sea fan. We show that mounded seep morphology results from sediment up-doming due to gas overpressure. Each of the seeps hosts its own gas pocket underneath the domes which are fed with methane of predominantly microbial origin along narrow pipes